Numerical Simulation Of Seepage Characteristics And Ion Exchange Reaction In Leaching Process Of Ionic Rare Earth Ore

Ionic rare earths are high-quality rare earth minerals with significantly strategic status only detected in China,which contain a complete range of medium and heavy rare earth elements with high value and have wide applications in various fields.However,the long-term rough mining has led to sharp decline of rare earth resources.Although the leaching process has been continuously studied and improved by researchers,there are problems still such as long leaching cycles and low leaching efficiency,which have seriously hindered the sustainable development and utilization of rare earth resources.As for the most important percolation and chemical reaction processes in the in situ leaching process,the current research mainly bases on experimental methods.However,the experimental methods can only obtain the data from the beginning and ends,which cannot numerically describe the flow phenomenon inside the packed bed.In addition,it is difficult to obtain the transient data of the reaction process.In order to be able to better describe the complex leaching process,this study adopts Computational Fluid Dynamics(CFD)modelling method and involves relevant basic theories such as hydrodynamics and chemical reaction kinetics to simulate the liquid-solid system in the percolation process and investigates the effects of varied parameter conditions on the percolation process and ion exchange reaction,the main conclusions are as follows:(1)The numerical simulation based on CFD method can accurately describe the fluid flow in porous medium,which is in good agreement with the experimental results,an average error about 7%.The energy loss caused by the fluid flowing through the porous medium increases with the increase of the flow velocity,and the law can be expressed by a linear fitting formula:h_f=26.16v-0.008.When the flow velocity keeps same,the larger the porosity of the porous medium and the larger the particle size,the smaller the corresponding hydraulic gradient.The seepage would deviate from Darcy’s linear law when the flow rate is larger.(2)The packed particles pattern affects the percolation process of porous medium.The closer the particles packed,the smaller the energy loss during percolation under the same number of packed particles.The energy loss is different in the percolation under packed varied shape particles.It is larger when the particle has larger surface contact along the inlet flow.(3)The developed CFD model considering chemical reaction kinetic can describe the leaching process of ionic rare earth ore more accurately,which is well consistent with the experimental results with an 11.2%average error.The solid phase volume fraction of ionic rare earth decreases after leaching reaction;it descreases by 10.2%after leaching 600 minutes.The larger solid phase porosity,the smaller leaching rate.Especially,the porosity of rare earths minerals increases 26%leading to 12%descrease for leaching rate.Although the larger inlet flow rate of leaching agent would contribute to larger leaching rate of rare earths,the optimal inlet flow rate is recommended to be between 0.004 m/s and 0.006 m/s in order to avoid wasting leaching agent.